Curious

[skdvr]

Earlier this week I went to a presentation by Richie Kohler on rebreathers. Basically he was talking about how great they are and why they are used for diving. I know that there are a TON of different breathers out there and there are a few of you on this board that dive them. I am just curious about a couple of questions.

1. What made you decide to switch from OC to CCR/SCR

2. Why did you decide on the unit that you bought?

3. Is there anything in your progression that you would have changed given the chance? Such as is there something you wish you had done more or less of before making the transition.

4. How about mCCR or eCCR? Which are you diving and why?? If you bought one type, do you wish you would have gotten the other?

5. If you tried them out and just did not like them at all I would be interested in hearing about that as well....

The amount of diving that I do right now just does not justify the cost of one right now. BUT, I do find them very interesting and can see myself with one at some point down the line.

If I had the money burning a hole in my pocket right now, to buy a breather, training, computers, and all other assorted gear I am not sure where I would go. Part of me like the Inspiration, because there is local training, and several other divers with them. I have been reading a lot about the rEvo and I think that is a very interesting breather, and is probably at the top of my list at the moment. Never really heard a bad thing about KISS either... I am sure that it is like anything, if you own one and have had good experiences with it then it is the greatest thing ever...

My knowledge of rebreathers is VERY limited, as I have only seen a few of them, and only read info about them on manufacturers websites and on forums. So if your answer get to technical for me, please pardon my silly return questions....:D

Thanks
Phil

[ppo2_diver]

Hi Phil,

I did one of the rebreather experience workshops a couple months ago and here is my thoughts on the overall switch to a rebreather. Joel Silverstein once said that rebreathers are designed to kill people. It is the responsibility of the rebreather "pilot" to minimize those risks. I have found that I am not pushing the limits of open circuit. Even for my technical dives, I'm staying in the 200 foot range. So the benefits of the rebreather do not outweigh the risks. If I were regularly doing 300+ foot dives and spending hours in the water, that would be another story. I also don't buy into the story that a rebreather will save me money on helium. Over time, maybe. But some may disagree, I feel my life is worth the extra few hundred dollars a year for OC helium.

I also have questions about the bailout options that are being taught. I've read about people doing a 200+ foot dive and only carrying a single AL40 with bottom mix for bailout and deco. Certainly not something I'd be comfortable doing.

It was a good experience, I learned a lot, and I would encourage people to try one out. The technology is cool and I enjoy reading about it, but I mostly likely won't be applying it anytime soon.

[skdvr]

Thanks for the input Duane... One of the things that Richie was talking about was the ability to do longer dives without the deco obligations. That was one of his benifits to using a RB on shallower dives of 150 and less. I can buy that. I do think that is a nice benifit to them. He was also pointing out about being clear of residual gas quicker than OC guys. I know absolutly nothing about that so I have no idea how accurate that is. I am with you on the OC trimix too. He was talking about the cheaper fills too, but that is at a much higher initial cost. I think he said that if you were doing about 20 or 25 trimix dives a year that you would pay for a RB in 4 or 5 years. I did not do the math so I have no idea how accurate that is or is not.

If I was making the switch it certainly would not be because I thought that the diving was going to be cheaper. You still have just as many regs to service each year, plus the extra RB servicing...

On the bail out issue, he did say that you need to carry enough OC to cover you for your planned dive. So the only weight saved would be the weight on your back, your OC bottles will probably be about the same. I can see planned no deco dives on RB with an AL40 but that is about it for only carrying a 40...

Thanks again...

Phil

[DeepDiverBob]

one other plus I have heard rebreather divers talking about is they keep you warmer when diving cold water.

Like Duane mentioned, some people call them death traps. But people also say that about diving trimix, caves and wreck penetration. At some point, every individual diver has to make the call when the risk no longer is worth the reward.

I am not sure about other manufacturers, but I know if you attend a DiveRite tech tour, you can demo their Optima rebreather. There is usually a small charge to demo it, but it is still fun to try.

[skdvr]

one other plus I have heard rebreather divers talking about is they keep you warmer when diving cold water.

Yeah, Richie mentioned that as well. Warm moist air... I can see where that would be nice when you are in cold water for a long time.

Like Duane mentioned, some people call them death traps. But people also say that about diving trimix, caves and wreck penetration. At some point, every individual diver has to make the call when the risk no longer is worth the reward.

I agree with that... Good Point....

I am not sure about other manufacturers, but I know if you attend a DiveRite tech tour, you can demo their Optima rebreather. There is usually a small charge to demo it, but it is still fun to try.

I will have to keep my eyes and ears open....

Thanks
Phil

[DeepDiverBob]

I will have to keep my eyes and ears open....

Thanks
Phil

TechTour will be at Haigh and Mermet in September.

[ppo2_diver]

Bob beat me to it. Dive Rite does come to Haigh and have a demo day. Last year they brought the Optima. I think it was only $25 to test dive it.

[scububa]

Finally a topic I know absolutely nothing about!

But, of course that won't stop me from posting :-)

Actually, what I heard Duane say was that they were designed to kill you and your (pilot) task was to manage the risk. I thought the analogy was a good one. I immediately thought of airplanes, as the key pilot word would invoke. It seems that the same parallel could apply. High tech, very unforgiving, loaded with things that can go wrong, performing a pretty 'unnatural' act but, when used properly, a great benefit.

On the life cycle costs - seems the cost of absorber, batteries, sensor cells all have to factor in. Of course, I guess it is somewhat offset by the reduced amount of beer you would have to buy, since you'd be in the water more.

[skdvr]

I guess it is somewhat offset by the reduced amount of beer you would have to buy, since you'd be in the water more.

I did not think of that one... Maybe I will buy one....;)

Phil

[theskull]

. . . Joel Silverstein once said that rebreathers are designed to kill people. . .

And Joel now dives a rebreather, at least for his deeper dives. Then again, Joel is in Richie's class, or maybe the other way around, so they are doing depths and durations that swing the benefit a little higher.

Still of no interest to me, but I haven't been much past 200 ft. and never intend to go deeper than 250 or so.

theskull

[skdvr]

never intend to go deeper than 250 or so.

theskull

Didn't you at one point never intend to go into a cave? Or was that DDB?

Phil

[theskull]

Didn't you at one point never intend to go into a cave? Or was that DDB?

Phil

LOL! Probably true of both of us.

With current technology and practices . . .

Dives to 300+ have much higher risk of DCS; when I chat with the guys who do these dives regularly, nearly all have had symptoms if not a chamber ride or two.

Rebreather incidents are much too common for my taste, and the amount of maintenance/preparation necessary is also more than I care to do routinely.

. . . so I'll reserve my options for advances in gear and science, but for now I'm sticking to 250 max and open circuit.

theskull

[DeepDiverBob]

and never intend to go deeper than 250 or so.

theskull

I remember sitting on OW class, when they were telling me about AOW class, and how that would certify me to go to 100 foot, and I said I would never have any reason to go that deep, 60 is good for me.

[scububa]

That is my problem with the RBs, also.
Too high a rate of incidents (to people with mega-experience).
Too much observation of an unacceptable (to me) level of futzing to get (or try to get) ready for a dive.
Too much 'marginal' behavior with accepting the units readiness to employ.
Still have to carry mucho gasso to dive within my level of comfort.
Too expensive.

That "what are your intentions" or "what were your intentions" is probably a vary interesting thread in itself, or a poll, or a topic for behavorial science research.

[SLIM]

Once you go to a RB, you need to make that your primairy dive equipment. Yes I do have a Custom made PSCR. It is designed differnat form all others and was built for particuler diving. It can be taken to any depth you want but you have to pay ver close attention about your gas mix.

There is added guagges to pay attention to.

I can go on and on with a list but is much easyer to show and describe in person.

Depending on what others have told you and you hear, you have to make the commitment yourself. Many I know have gotten trained on several sifferant ones before they decided to bye. Each design being a PSCR, ECCR, MCCR works the same principals for each catogory. Then each brand has its own small ideosencisies thta you must learn. I have just go to a PSCR just over a year ago and been a tester for the design I use. There are many reasons I like it over others.

Yes, many RB divers do not take enough gas for them, they learn that a team bailout. There are many differant modes of thought to this.

Go to all the places you can try them out, take as many classes as you can. Talk to everyone you can and lok at them. If you ever make it down, I can arrange for a day of a short class to try one brand out.

Remember as it wsa said earler, you are a pilot and flying thesystem and trust to more then just looking at guages. So many more things to be constantly looking at and reading.

As Bubba said, many have died even experianced divers.

I do have some factual information I can say I had the persons that they have had problems and the close calls I can tell you about. I even lost a cave buddy in September from a RB.

SLIM

[skdvr]

Again I kind of go back to my skydive thinking... Most of the fatal accidents are from very experienced jumpers that are either pushing the limits, or they get complacent and just do not pay as much attention as they need to. The more experienced guys are generally flying much higher performance parachutes that have to be watched every second or they can get away from you. If someone flying a bigger slower parachute has a brain fart they are coming down much slower and may only bruise their ego a bit.

So now back to RB. One point that I have heard is that they require more attention from the diver before, during, and after the dive. If you are the type of person that like to throw your gear in a bag and leave it there until your next dive, then maybe a RB is not a good choice for you. They are not as simple as just throwing them on your back and getting into the water. Honestly that is one of the things that I think is drawing me to them.

So lets say that I had already bought one and training was done... Is it something that should be dove even for shallow dives of say 30 ft in a local quarry by me? Maybe just do that until you have some hours on the unit. I know that the first class only takes you to 130 or there about and you have to have so many hours before you can go to the next level of training.

I would be interested in checking out your RB the next time I am down there... I was hoping to get down there in March for some diving, but we will see.

Thanks again for all the responses...

Phil

[brettbyers]

I've been looking into RB also.The main benifits that I am attracted by are length of time you can stay at depth without accumulating a lot of deco and the fact that RBs keep your core temp a lot warmer so those hour dives in Lake Michigan can now turn into hour and one half dives. Money is a big factor so RBs are only an interest at this time. Maybe in a year or two.

[vtach67]

I switched to a CCR for a combination of reasons.

1. Less equipment to haul
2. Less weight on your back
3. Gas logistics for deep dives.
4. Decompression advantages
5. Less helium use.
6. Breathing warm moist gas. (Yes, I think you do stay warmer)
7. I like the technology.

I don't think that any of these reasons alone justifies the purchase of a CCR but for me, the combination made a pretty strong argument.

I picked a VR/CCRB Sentinel (eCCR). I wanted back mount CL, packable scrubber, and well thought out electronics package with predive and sensible alarms. My second choice would have been the KISS Classic. No interest in the Inspo/Evo, Optima or Meg because of over the shoulder CL's.

I would not have changed any of the progression I made on OC and would recommend anyone moving on to CCR to have a minimum of Adv Ntx/Deco with a strong recommendation for entry trimix and at least 20-30 REAL deco dives. The primary reason is for the mastering of buoyancy, stops, gas switches and understanding of gas mixes/PO2..etc..

I don't have a preference for mCCR or eCCR but I do think that eCCR is easier to become complacent on. I think a HUD should be mandatory equipment on both.

The two biggest reasons for people dying on CCR are
1. Diving a unit with known problems or little maintenance
2. Medical..

These units need maintenance which is not that time consuming or difficult. I have spent more time blending OC gas than I do prepping or cleaning my CCR. When people don't take care of their unit or stretch the life of their scrubber....see reason #1.

Also, you are working to breath on these units. It is not like cracking the diaphragm on a positive pressure gas delivery system. You need to be in good cardiovascular health or the potential for problems is much higher.

When you recognize and continually remind yourself of the limitations of these units, I believe that you have greatly reduced the likelihood of problems. The rest is proper dive planning, training and repeated practice. I am not afraid to thumb a dive even for small questionable issues. My life is worth it. Also, When in doubt BAIL OUT!! You can always try to go back on the loop with a clear head and manage a problem if you need to but if you are at all compromised (hypoxic or hypercapnic), you are asking for more problems.

[brettbyers]

I picked a VR/CCRB Sentinel (eCCR). I wanted back mount CL, packable scrubber, and well thought out electronics package with predive and sensible alarms. My second choice would have been the KISS Classic. No interest in the Inspo/Evo, Optima or Meg because of over the shoulder CL's.


I'm new to RBs so I don't understand a lot of the acronyms. What is an over the shoulder CL?

I don't have a preference for mCCR or eCCR but I do think that eCCR is easier to become complacent on. I think a HUD should be mandatory equipment on both.


What is the diference between a mCCR and a eCCR? What is a HUD?

[skdvr]

CL = Counter Lungs

mCCR = Manual CCR - You manually add O2 into the loop to keep your PPO2 at the level that you want.

eCCR = Electronic CCR - There is an onboard controller that makes sure your PpO2 stays where it is supposed to

HUD = Heads up Display - Usually a series of lights that will attach to the mouthpiece or somewhere else that you can see. You can either be notified of what is going on by different combinations of flashing lights, or it could be a simple Green/Red. Green means everything is good to go and red means that something is outside of set parameters and needs your attention.

That is about as much knowledge as I have about them, or should I say that I think I have about them. Hopefully that is correct. If not I am sure I will be corrected.

Todd -Have you seen or read anything about the rEvo? It sounds like a very well put together RB, and has been getting some good reviews from what I can tell...

Here is a link to its owners manual if anyone has any interest in reading it
rEvo II Manual (http://www.revo-rebreathers.com/Manual%20rEvo%20II%20v1.0%20en%20022007.pdf)

Phil

[vtach67]

Brett, the CL or counter lungs are the flexible "breathing bags" of the system. Some units have them mounted at your back and others have them mounted over your shoulder. Most of the units with OTS (over the shoulder) CL's have felt very cluttered in the chest area so I prefer the BMCL (back mount counter lung).

The common denominator with manual CCR's is a constant flow orifice or also known as a "leaky valve". The idea is that there is a constant flow of oxygen streaming into the unit. The flow rate is set just below what you would normally metabolize on an average dive. The PO2 will gradually drop and you manually supplement it to keep whatever you decide to keep your PO2 at. Some people are adding an adjustable metered flow device to these units to manually adjust the oxygen flow at depth.

Yes I have seen the rEvo. Kevin Ward (Fireman on RebreatherWorld) has one and he lives in Chicago. I dove with him while he was on it. It seems like a nice unit and is well put together. It has some idiosyncracies that I am not to keen upon like the manual add buttons are at the base of the unit and the handsets are activated by tapping them in a sequence. It also does not come with a BOV (bailout valve-OC reg built into the mouthpiece) standard. Overall though, I think those are minor things and the unit is very capable, upgradeable and has good support from the manufacturer.

[skdvr]

Yes I have seen the rEvo. Kevin Ward (Fireman on RebreatherWorld) has one and he lives in Chicago. I dove with him while he was on it. It seems like a nice unit and is well put together. It has some idiosyncracies that I am not to keen upon like the manual add buttons are at the base of the unit and the handsets are activated by tapping them in a sequence. It also does not come with a BOV (bailout valve-OC reg built into the mouthpiece) standard. Overall though, I think those are minor things and the unit is very capable, upgradeable and has good support from the manufacturer.

I have head that complaint from several people... Then others say they would not have it any other way.... I guess it is all in what you get use to.

Thanks again for all the info...

It is greatly appreciated.

Phil

[skdvr]

Below is a quote from info on the Hybrid rEvo. I only pasted a portion that I have questions about. I do not exactly understand why the unit is limited to 80m in anything but full eCCR.

If you want to read the whole thing here is the link
http://www.revo-rebreathers.com/The%20rEvo%20Hybrid%20CCR.pdf

eCCR with orifice bleeding:
Both the orifice and controlled valve are used, and the diver uses the high setpoint:
the PPO2
is maintained constant by the controller, but the valve must inject much less because during
quite diving nearly all the oxygen needed to maintain metabolic consumption, is supplied by
the bleeding orifice. (This means the battery use of the solenoid will only be a fraction of the
normal pure eCCR mode).
This mode can be used up to max 80 meters, because the absolute pressure of the oxygen first
stage is kept constant, even by increased depth.
pure eCCR:
When the diver wants to go deeper than 80m, the previous modes can not be used any more,
because when the orifice is used, the 1 st stage must be transformed into an absolute pressure
regulator: this way the pressure will not increase when the diver descends. But reaching 80m,
the intermediate pressure comes nearer to the absolute pressure in the water, and so nearly no
more pressure is available for the orifice and the valve, and no more oxygen can be added to
the loop. When going deeper than 80m, the 1 st stage must be transformed again to a standard
regulator (by simply taking off the absolute pressure cap), and the orifice must be blocked
(with the same plug that is used to block the valve in the pure mCCR mode), if not the flow
trough the bleeding orifice would increase by greater depth, become higher than the metabolic
consumption, and make the breathing gas hyperoxic.
When this done (no absolute pressure cap on the regulator, and the orifice blocked), the rEvo
works as a pure eCCR, with low and high setpoint, and all needed oxygen is supplied by the
electronically controlled valve. The manual addition valves are still there to add any gas to the
loop when needed. There is no more depth limit because of the absolute intermediate
pressure, but rEvo advises to use the unit not deeper then 100m.

Is it because if you are using the bleeding orfice teh pressure will be to great below 80m for O2 to flow into the loop?? How far off base am I here. I just cant seem to make sense of it...

Thanks

Phil

[vtach67]

Yes. When the pressure at depth reaches equilibrium with the IP of the O2 "blocked" first stage, no more O2 flows hence the reason for the depth limit on manual/hybrid mode.

[skdvr]

Yes. When the pressure at depth reaches equilibrium with the IP of the O2 "blocked" first stage, no more O2 flows hence the reason for the depth limit on manual/hybrid mode.

Thank You...

Phil

[skdvr]

Question - What is the difference between the radial and axial scrubbers???

Thanks
Phil

[vtach67]

Question - What is the difference between the radial and axial scrubbers???

Thanks
Phil

The flow in an axial scrubber is top to bottom or vice versa. The flow in a radial scrubber is inner to outer or vice versa. There is quite a bit of debate as to which is more efficient. I don't think that you can easily say one is better than the other without taking a close look at the design of the whole unit itself. Just insulating the scrubber can effect its efficiency. Generally speaking, the more heat retained, the more efficiency out of the scrubber. So there is really more to the picture than just the design of the scrubber gas flow. Just my opinion on that.:)

[skdvr]

Ah that seems to make sense... I have read a lot that people think one is better than the other for this reason or that reason, but I just could not seem to find anything about What they were...

Thank you for clearing that up...

Phil